The invention relates to a contact spring and a contact base.
Contact bases of this kind include a plurality of contact springs, to which the pins (legs) of electronic components, particularly semiconductor components with integrated circuits (ICs), may be fitted in order to establish an electrical connection with an electronic device to which the contact socket is connected. An electronic device of such kind may be for example a test device having an electronic computing apparatus, which is used to test the function of the components before they are mounted on printed circuit boards or other substrates. In this context, the contact bases are typically secured to a panel-like contact base holder arranged on the tester, while the electronic components are advanced via an automatic handler, pressed against the contact springs of the contact base, and then removed from the contact bases when the test operation is completed so that the components can be sorted according to the result of the test.
As may be seen in FIGS. 8 and 9, on known contact bases the contact springs 1 used have a tip with a pitched cap and a contact blade 2 extending transversely. FIG. 8 also shows an end section of a pin 3 of an electronic component (IC). If an electronic component and thus also pins 3 of such component are fitted against assigned contact blades 2 of the contact springs in the direction of arrow 4, which indicates the infeed direction, the entire length of contact blade 2 is contact with pin 3. However, it is been found that, after long periods of use and a correspondingly large number of contacting operations, deposits are formed on such spring tips and contact blades, causing the contact resistance between contact blade 2 and pin 3 to rise significantly. This is particularly true if lead is not used in the alloy that is used for the pin coatings. For environmental reasons, tin is often used for these pin coatings instead of lead, and the alloy is softer than one made with lead. This appears to encourage the formation of deposits 5. Accordingly, perfect contacting with low contact resistance between contact springs 1 and pins 3 can no longer be guaranteed over a large number of contacting operations.
EP 1 826 575 A2 discloses a contact element for use in a test device that may be mounted on the load board of a test apparatus: the contact element, which is used to establish contact between at least one connector of a component to be tested and a corresponding track conductor on the load board, has a first end that defines a plurality of contact points. When the contact element is rotated about an axis generally perpendicular to a plane defined by the contact element, contact is created with contact points on the component to be tested one after the other.
U.S. Pat. No. 5,599,194 discloses a contact pin having a thin wall construction that creates good electrical connection with an IC socket, but does not allow isolation to occur due to the build-up of an oxidation layer on the surface of the connector. Moreover, the contact pin does not break easily due to plastic deformation.
U.S. Pat. No. 5,461,258 discloses a socket for semiconductor elements that prevents foreign bodies from adhering to the fastening surfaces of the external connectors of a semiconductor element.
US 2008/0094090 A1 discloses a test head for use with a base having small pitches that does not require cleaning. This is achieved by the provision of a z-shaped zone that is deflected elastically in a vertical direction, and a zΘ-shaped zone that is connected in series to the z-shaped zone and rotates while elastic deflection takes place at least in the vertical direction.